Phase Doubling and Entanglement Generation in Coherent Matter-Wave Reactions

Chemical reactions in a statistical ensemble are conventionally regarded as incoherent processes driven by thermodynamics. In the classical regime, reactions are expected to proceed faster at high temperatures and slow to a halt in the zero-temperature limit according to Arrhenius kinetics. In the quantum degenerate regime, where bosonic atoms and molecules form coherent matter waves, reactions are instead described by nonlinear mixing of matter-wave fields, leading to collectively-enhanced reaction rates and coherent amplification. This raises the question: how does the matter-wave phase evolve during a reaction, and how can it influence reaction dynamics? In the quantum regime, the matter-wave phases of the reactants and products are expected to match through wave mixing, analogous to phase matching of photonic fields in nonlinear optics.\par We report the observation of phase coherent reaction dynamics of Bose-condensed atoms and molecules near a Feshbach resonance. Using matter wave diffraction with optical lattices, we verify spatial coherence of both reactants and products and observe phase doubling when atomic waves combine into molecular waves - the matter-wave analogue of second-harmonic generation. The diffraction patterns also reveal distinct signatures of entanglement generated between reacting particles as the reaction is initiated. Our observations establish phase coherence and entanglement as two essential features of "quantum many-body chemistry" where macroscopic quantum fields govern the reaction dynamics.Chemical reactions in a statistical ensemble are conventionally regarded as incoherent processes driven by thermodynamics. In the classical regime, reactions are expected to proceed faster at high temperatures and slow to a halt in the zero-temperature limit according to Arrhenius kinetics. In the quantum degenerate regime, where bosonic atoms and molecules form coherent matter waves, reactions are instead described by nonlinear mixing of matter-wave fields, leading to collectively-enhanced reaction rates and coherent amplification. This raises the question: how does the matter-wave phase evolve during a reaction, and how can it influence reaction dynamics? In the quantum regime, the matter-wave phases of the reactants and products are expected to match through wave mixing, analogous to phase matching of photonic fields in nonlinear optics.\par We report the observation of phase coherent reaction dynamics of Bose-condensed atoms and molecules near a Feshbach resonance. Using matter wave diffraction with optical lattices, we verify spatial coherence of both reactants and products and observe phase doubling when atomic waves combine into molecular waves - the matter-wave analogue of second-harmonic generation. The diffraction patterns also reveal distinct signatures of entanglement generated between reacting particles as the reaction is initiated. Our observations establish phase coherence and entanglement as two essential features of "quantum many-body chemistry" where macroscopic quantum fields govern the reaction dynamics.

Jan 1, 20260 citations

Shu Nagata

Jun 1, 20260 citations

Observation of phase doubling and entanglement in coherent matter-wave reactions

Shu Nagata, Tadej Mežnaršič, Chuixin Kong +1 more

Chemical reactions in a statistical ensemble are conventionally regarded as incoherent processes driven by thermodynamics. In the quantum degenerate regime, where atoms and molecules form coherent matter waves, reactions are theoretically described by nonlinear mixing of matter-wave fields. In this scenario, we expect phase matching between reactants and products, analogous to the mixing of photonic fields in nonlinear optics. Here we report on the observation of phase coherent reaction dynamics of Bose-condensed atoms and molecules near a Feshbach resonance. Using matter-wave diffraction with optical lattices, we verify spatial coherence of both atoms and molecules and observe phase doubling when atomic waves combine into molecular waves, the matter-wave analogue of optical frequency doubling. The diffraction patterns further reveal two-atom entanglement generated during the reaction. Our observations establish phase coherence and entanglement generation as two essential features of "quantum many-body chemistry". Moreover, our work opens a pathway to control of reaction dynamics by manipulation of matter-wave phases.Chemical reactions in a statistical ensemble are conventionally regarded as incoherent processes driven by thermodynamics. In the quantum degenerate regime, where atoms and molecules form coherent matter waves, reactions are theoretically described by nonlinear mixing of matter-wave fields. In this scenario, we expect phase matching between reactants and products, analogous to the mixing of photonic fields in nonlinear optics. Here we report on the observation of phase coherent reaction dynamics of Bose-condensed atoms and molecules near a Feshbach resonance. Using matter-wave diffraction with optical lattices, we verify spatial coherence of both atoms and molecules and observe phase doubling when atomic waves combine into molecular waves, the matter-wave analogue of optical frequency doubling. The diffraction patterns further reveal two-atom entanglement generated during the reaction. Our observations establish phase coherence and entanglement generation as two essential features of "quantum many-body chemistry". Moreover, our work opens a pathway to control of reaction dynamics by manipulation of matter-wave phases.

arXiv:2505.20581Reports on Progress in PhysicsMay 29, 20261 citation

Many-body chemical reactions in a quantum degenerate gas

Zhendong Zhang, Shu Nagata, Kai-Xuan Yao +1 more

Abstract Chemical reactions in the quantum degenerate regime are described by mixing of matterwave fields. Quantum coherence and bosonic enhancement are two unique features of many-body reactions involving bosonic reactants and products. Such collective reactions of chemicals, dubbed “super-chemistry”, is an elusive goal in quantum chemistry research. Here we report the observation of coherent and collective reactive coupling between Bose condensed atoms and molecules near a Feshbach resonance. Starting from an atomic condensate, the reaction begins with a rapid formation of molecules, followed by oscillations of their populations in the equilibration process. Faster oscillations are observed in samples with higher densities, indicating bosonic enhancement. We present a quantum field model which describes the dynamics well and identifies three body recombination as the dominant reaction process. Our findings exemplify the highly sought-after quantum many-body chemistry and offer a new paradigm for the control of quantum chemical reactions.Abstract Chemical reactions in the quantum degenerate regime are described by mixing of matterwave fields. Quantum coherence and bosonic enhancement are two unique features of many-body reactions involving bosonic reactants and products. Such collective reactions of chemicals, dubbed “super-chemistry”, is an elusive goal in quantum chemistry research. Here we report the observation of coherent and collective reactive coupling between Bose condensed atoms and molecules near a Feshbach resonance. Starting from an atomic condensate, the reaction begins with a rapid formation of molecules, followed by oscillations of their populations in the equilibration process. Faster oscillations are observed in samples with higher densities, indicating bosonic enhancement. We present a quantum field model which describes the dynamics well and identifies three body recombination as the dominant reaction process. Our findings exemplify the highly sought-after quantum many-body chemistry and offer a new paradigm for the control of quantum chemical reactions.

arXiv:2207.08295Nature PhysicsJul 24, 202331 citations

Coherent bimolecular reactions with quantum-degenerate matter waves

Hui Jing, Jing Cheng, Pierre Meystre

We demonstrate theoretically that the abstraction reaction $A+{B}_{2}\ensuremath{\rightarrow}AB+B$ can be driven coherently and efficiently with quantum-degenerate bosonic or fermionic matter waves. We show that the initial stages of the reaction are dominated by quantum fluctuations, resulting in the appearance of macroscopic nonclassical correlations in the final atomic and molecular fields. The dynamics associated with the creation of bosonic and of fermionic dimer-atom pairs is also compared. This study opens up a promising regime of quantum-degenerate matter-wave chemistry.We demonstrate theoretically that the abstraction reaction $A+{B}_{2}\ensuremath{\rightarrow}AB+B$ can be driven coherently and efficiently with quantum-degenerate bosonic or fermionic matter waves. We show that the initial stages of the reaction are dominated by quantum fluctuations, resulting in the appearance of macroscopic nonclassical correlations in the final atomic and molecular fields. The dynamics associated with the creation of bosonic and of fermionic dimer-atom pairs is also compared. This study opens up a promising regime of quantum-degenerate matter-wave chemistry.

arXiv:0902.3797Physical Review AFeb 20, 20093 citations

Quantum interference and entanglement in ultracold atom-exchange reactions

Yi-Xiang Liu, Lingbang Zhu, Jeshurun Luke +4 more

Coherent superpositions and entanglement are hallmarks of quantum mechanics, but they are fragile and can easily be perturbed by their environment. Selected isolated physical systems can maintain coherence and generate entanglement using well-controlled interactions. Chemical reactions, where bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Here we investigate this question by studying the 2KRb $\rightarrow$ K $_2$ + Rb $_2$ reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.Coherent superpositions and entanglement are hallmarks of quantum mechanics, but they are fragile and can easily be perturbed by their environment. Selected isolated physical systems can maintain coherence and generate entanglement using well-controlled interactions. Chemical reactions, where bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Here we investigate this question by studying the 2KRb $\rightarrow$ K$_2$ + Rb$_2$ reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.

arXiv:2310.07620Oct 11, 20231 citation

\rightarrow

_2

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reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.